Call conversion method and call forward system based on SIP protocol

The method is used for switching over the calls based on IP phone attendant console system and the core network controller. The IP phone attendant console comprises an attendant console server, an attendant console client side and a media server. The three above are connected via IP connection; the communication protocol uses SIP protocol; the core network controller is used to control the access of all user ends and cooperates with the IP attendant console system to provide calling and switching functions, and is connected to the attendant console server via IP connection, and uses SIP protocol to exchange signaling with the attendant console server. Wherein, when the calling user makes call with the attendant console client side, the attendant console client side calls the called user; the attendant console server indicates the core network control to establish the call connection between the calling user and called user. The invention leads all switching services in PSTN network into the NGN network.